1. Field of the Invention
The present invention relates to an optical system for a Fresnel lens light, particularly a spotlight or floodlight, with an ellipsoidal reflector, a light source and at least one Fresnel lens and to a Fresnel lens light with the optical system.
2. Description of the Related Art
Conventional optical systems for Fresnel lens lights include a light source, a Fresnel lens and spherical auxiliary reflector as the lighting engineering relevant parts. The filament of the light source is located substantially unchanged at the focal point of the spherical auxiliary reflector. Because of that a portion of the light radiated from the light source is reflected back to it and assists the light to the front of the light. The Fresnel lens focuses the light radiated in the front direction. The extent of the focusing depends on the distance between the Fresnel lens and the light source. If the filament is located at the focal point of the Fresnel lens, the narrowest light beam is produced or propagated. In that case a quasi-parallel beam, also known as a spotlight, is obtained. By shortening the distance between the Fresnel lens and the light source, the aperture angle of the propagated light beam continuously increases. In that case a divergent beam, also called a floodlight, is obtained.
This type of light has the disadvantage of a poor light efficiency, especially in the case of the spotlight, since the Fresnel lens receives light from the light source only over a comparatively small angular range. Furthermore it is disadvantageous that a large part of the light reflected by the spherical reflector impinges on the filament of the light source, is absorbed there and further heats the filament.